708 EEPORT — 1894. 



waves arriving' from opposite directions, or from tlie rebound of the tidal veavcs 

 from otlier coasts. 



Tliis effect, also, it Las been so far found impossible to predict without observa- 

 tion. On our southern coasts, for instance ; in the western part the tide rises about 

 15 feet, but as it travels eastward the range becomes less and less until, about 

 Poole, it reaches a minimum of 6 feet. Fartlier east again it increases to Hastings, 

 -where the range is 24 feet. Yet farther east it again gradually diminishes. This 

 is due to the reflection from the French coast, which brings another wave which 

 either superposes itself upon, or reduces the effect of, the main tide advancing up 

 the English Channel; but the details of such reflection are so complex that no 

 one could forecast them without more knowledge than we possess. 



There can be little doubt that to tbis cause, reflection, is mainly due ths 

 variations in the amount of mean range of tide which are iound on many coasts 

 at different parts ; and as these reflected waves may arrive from great distances, 

 and be many in number, we may cease to wonder at the extraordinary differences 

 in range of tide which prevail, though it will be understood that this is wholly 

 separate from the varying heights of each successive tide, or of the tide at 

 different parts of each lunation, or at different times of the year, which depend 

 upon the astronomical influences. 



The actual height of the tide in deep water is small, but on passing into shallow 

 water when approaching a shore, and especially when rolling up a gulf of more or 

 less funnel shape, it becomes increased by the retardation caused by friction, and 

 by compression laterally, and hence the height of the tide on a coast aft'ected by 

 other causes is greater than in the open sea. 



The oceanic tide wave is supposed to be from 2 to 3 feet in height, hut as this 

 has been assumed from observations made at small oceanic islands where, although 

 the magnifying influences mentioned are at a minimum, they still exist, we wait 

 for precise information until some means of actually measuring the tide in deep 

 water is devised. 



The waves due to wind, though not so far-reaching in their effects as the 

 majestic march of the tide wave, are phenomena which are more apparent to the 

 traveller on the ocean. 



The deep sea in a heavy gale presents, perhaps, the most impressive manifesta- 

 tion of the powers of Nature which man can behold, and doubtless many of us 

 have experienced feelings that may vary from awe and wonder to sheer delight, 

 .according to the temperament of each individual, at for thy first time finding himself 

 face to face with this magnificent sight, though I rather fear that discomfort is the 

 prevailing feeling that many carry away. 



The height to which storm waves may rise has never been very satisfactorily 

 determined. Apart from the difficidty of the task and the small number of people 

 who will address themselves to it when they have the chance, it is but rarely that 

 any individual sees really abnormal waves, even though he may be at sea all his 

 life. 



Different heights for what are called maximum waves have been recorded, and 

 they vary from 40 to 90 feet from crest to hollow. 



All we can sa}' is that the most probable figure is about 50 or 60 feet. 



These great storm waves travel very far. In some cases they convey a warning, 

 as their velocity always far exceeds that at which the storm is travelling. In others 

 they intimate that a gale of which no more is seen has occurred somewhere — it may 

 ,be many miles distant. 



When they have travelled beyond the limits of the wind which raised them, 

 they lose the steepness of slope which characterises them when under its influence, 

 ,and become an undulation which is scarcely noticed when in deep water. 



On approaching shallow water, however, they are again apparent, and the 

 ' rollers ' that occur unperiodically at various places in latitudes where gales never 

 occur would seem to be caused by such waves, originating in areas many thousands 

 of miles distant. Such appears to be the origin of the well-known rollers at 

 Ascension and St. Helena, where the rocky and exposed nature of the landing has 

 caused this phenomenon to be especially noticed. 



